The need for monitoring and managing large arrangements of electrochemical energy storage cells for various applications is known. Systems for performing such monitoring and management typically include features such as voltage measurement, temperature measurement and battery cell balancing (i.e. equalization) either through selective cell dissipative discharging or charge redistribution. Of particular interest are large-scale systems used for storing electrical energy for the propulsion of vehicles as well as energy storage systems for electrical grid support and supplying power to remote locations.
Various methods exist for attempting to verify the measurement data by examining its content to determine the plausibility of the information gathered. One method is to compare the sum of the cell voltages to the pack voltage. However, this method needs extremely accurate measurements. A 200 mV error might seem very small for a pack voltage, while it can be very large for a cell voltage. Other methods include checking the ranges of the measurements of the cells to ensure that they seem reasonable. This technique could catch issues where a reading is low enough or high enough to be unreasonable, but would not catch any errors in which a cell reading is replaced by a different cell's reading. Moreover, modern batteries have an increasingly minimal change in cell voltage as a function of depth of discharge, meaning that it is quite normal that a number of cells will appear to be (within the precision of the measurement system) at the same voltage over a large range of a system's lifetime.
A second method is known in the art, which suggests using two redundant measurement systems. However, this method may add significant cost to the monitoring solution.
Due to the architecture of a number of measuring circuits, there is often a great deal of shared componentry used to measure a number of cell voltages or temperatures. This is done to reduce the cost associated with large numbers of highly accurate components that a lack of sharing would impose, especially when a system contains a high number of cells.
Most large-format battery systems operated over a long period of time require cell balancing. This can be accomplished by selective cell charging, selective cell discharging, charge shuttling, or combinations of the above. A number of methods exist for these strategies.